Varying lepton efficiencies

Bug #1436948 reported by Jeff Asaf Dror
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
MadGraph5_aMC@NLO
Invalid
Undecided
Unassigned

Bug Description

Hi,

I've recently noticed that pythia-pgs has reduced lepton tagging efficiencies. I was wondering whether this was intentional. As a simple test I tried (with all default settings in SM file)
> generate p p > z, z > l+ l-
and running pythia-pgs. By checking the number of two lepton events in the final state in the LHCO file (8135 out of 10000) I calculate an efficiency of about 90%. This is in line with the value I expected.

However, if I run
> generate p p > z
and let pythia-pgs decay the Z I only find 319 out of an expected 688 events, corresponding to an efficiency of 68% (I've also ran this with higher statistics yielding similar results).

Is this an expected behavoir?

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) wrote :

Hi,

I have no idea and we will not be able to help you on this.
I would suggest that you contact the pythia author to know the difference of treatment between those two way to compute.

What is likely to be due to a difference of treatement in the invariant mass of the Z, Since in the first case the invariant mass is forced by a cut to be between +-15 times the width (the 15 number can be change in the run_card).
On the second case, MG generates the Z onshell, but it is likely that pythia changes the invariant mass.

Cheers,

Olivier

Changed in mg5amcnlo:
status: New → Invalid
To post a comment you must log in.
This report contains Public information  
Everyone can see this information.

Other bug subscribers

Remote bug watches

Bug watches keep track of this bug in other bug trackers.